Control circuits are utilized for controlling the duty cycle of a power transformer within a magnetic power converter system. The on time and off time of a power switch which controls energization of the primary winding of the power transformer within the system may be controlled by integrated circuitry using external references which detect variations across the load of the system in order to maintain the output voltage constant. Additionally, such control circuits require isolating elements, for example, optical couplers in order to couple the output on the secondary side of the transformer to the primary side. Such circuitry is costly and requires numerous circuit elements in order to perform the control operation.
A need has thus arisen for a control circuit for use in a magnetic power converter which provides for efficient operation, high performance, but which accomplishes the control function with minimal electronic components thereby decreasing the circuit cost and increasing reliability.